KR102528053B1 - Composite braze liners for low-temperature brazing and high-strength materials - Google Patents

Abstract

An apparatus, material and method for forming a brazing sheet has a composite braze liner layer of a low melting point aluminum alloy and a 4000 series braze liner. The low melting point layer of the composite braze liner facilitates low temperature brazing and reduces diffusion of magnesium from the core into the composite braze liner. Reduction in magnesium diffusion also results in good braze joint formation through the use of controlled atmosphere brazing (CAB) and Nocolok flux at low temperatures by lowering the formation of related magnesium oxides that resist removal by Nocolok flux at the braze joint interface. facilitate This equipment also enables the production of brazing sheet materials with high strength and good corrosion properties.

Description

Composite braze liners for low-temperature brazing and high-strength materials

The present invention relates to apparatus and methods for manufacturing heat exchangers, and more particularly to materials used to manufacture heat exchangers from aluminum alloy brazing sheets formed into heat exchanger components and integrated into an assembly by brazing. will be.

A variety of devices, materials and methods are known for manufacturing heat exchangers. Aluminum heat exchangers, such as radiators, condensers, heater cores, etc., are often assembled using brazing techniques including controlled atmosphere brazing (CAB) and vacuum brazing. In the brazing process, the braze liner layer of the composite brazing sheet is melted, for example by exposure to the high temperatures of a furnace, and converted into a filler metal to form a braze joint between heat exchanger components, such as tubes and headers, tubes and fins, etc. play a role

Low temperature brazing has been proposed to use a single layer of a braze alloy liner with a low melting temperature, but this has a negative impact on machinability, corrosion performance, joint strength, hardness, brittleness, and difficulty of roll bonding. Despite known methods, materials and devices, a need remains for alternative methods, devices and materials for manufacturing heat exchangers.

The disclosed subject matter relates to a sheet material comprising a core of 2XXX, 3XXX, 5XXX or 6XXX aluminum alloy; A composite braze liner having a low melting point aluminum alloy layer and a 4XXX aluminum alloy layer.

In another embodiment, the low melting point aluminum alloy has a lower melting point than the 4XXX aluminum.

In another embodiment, the 4XXX aluminum alloy is disposed on the core and the low melting point aluminum alloy is disposed on the 4XXX aluminum alloy distal to the core.

In another embodiment, the low melting point alloy is disposed on the core and the 4XXX aluminum alloy is disposed on the low melting point aluminum alloy distal to the core.

In another embodiment, the 4XXX aluminum alloy comprises a first 4XXX aluminum alloy layer and a second 4XXX aluminum alloy layer, the first 4XXX aluminum alloy layer disposed on the core and the low melting point aluminum alloy comprising disposed on the first 4XXX aluminum alloy layer distal to the core and the second 4XXX aluminum alloy layer disposed on the low melting point aluminum alloy layer distal to the first 4XXX aluminum alloy layer .

In another embodiment, it further includes at least one distal layer of an aluminum alloy disposed on the core on a side distal to the composite braze liner.

In another embodiment, said at least one distal layer is a 4XXX aluminum alloy layer.

In another embodiment, the at least one distal layer is a second composite braze liner.

In another embodiment, the at least one distal layer is a water side liner.

In another embodiment, the water side liner is a 7XXX aluminum alloy with 1.0 to 15 weight percent zinc.

In another embodiment, the low melting point aluminum alloy has a melting point in the range of 510 °C to 560 °C.

In another embodiment, the low melting point aluminum alloy includes 4.0 to 12.0% by weight of Si, 0.1 to 1.0% by weight of Fe, 1.0 to 5.0% by weight of Cu, and 5.0 to 20.0% by weight of Zn.

In another embodiment, the low melting point aluminum alloy has a solidus line in the range of 510°C to 560°C and a liquidus line in the range of 565°C to 585°C.

In another embodiment, the amount of Si in the low melting point aluminum alloy ranges from 4 to 9 weight percent.

In another embodiment, the amount of Zn in the low melting point aluminum alloy ranges from 6 to 18 weight percent.

In another embodiment, the composite braze liner comprises 4.0-12.0 wt% Si, 0.1-1.0 wt% Fe, ≤2.0 wt% Cu, 1.0-6.0 wt% Zn, wherein the composite braze liner is 515 It has a solidus line from °C to 575 °C and a liquidus line from 565 °C to 595 °C.

In another embodiment, the composite braze liner includes 10.0 to 10.5 wt% of Si, 0.15 to 2.0 wt% of Fe, ≤0.7 wt% of Cu, ≤4.0 to 6.0 wt% of Zn, and the composite braze liner includes: has a solidus line of 550 ° C to 575 ° C and a liquidus line of 575 ° C to 590 ° C.

In another embodiment, the core comprises 0.10-1.2 wt% Si, 0.15-0.5 wt% Fe, 0.40-3.5 wt% Cu, 0.10-1.8 wt% Mn, 0.20-1.85 wt% Mg, <0.01 Cr, ≤0.20% Zn, and ≤0.20% Ti, by weight, the core has a solidus of >590°C and a liquidus of >650°C.

In another embodiment, the core comprises 0.10-0.90 wt% Si, 0.15-0.5 wt% Fe, 0.40-2.60 wt% Cu, 0.10-1.55 wt% Mn, 0.20-1.0 wt% Mg, <0.01 Cr in weight percent, ≤0. 0.20% by weight of Zn, and ≤0.20% by weight of Ti, the core has a solidus of >590°C and a liquidus of >650°C.

In another embodiment, the core includes at least one strengthening element selected from Si, Cu, Mn and Mg.

In another embodiment, Mg present in the core (pre-braze) is in an amount of 0.2 to 1.85 wt%, Cu is in an amount of 0.4 to 3.5 wt%, Mn is in an amount of 0.1 to 1.8 wt%, and Si is in an amount of 0.1 wt%. to 1.2% by weight.

In another embodiment, the clad ratio of the composite braze liner to the core ranges from 4 to 18%.

In another embodiment, in the composite braze liner, the ratio of the thickness of the low melting point aluminum alloy to the thickness of the 4XXX aluminum alloy ranges from 5 to 50%.

In another embodiment, the LPM liner and 4000 liner are roll bonded and manufactured separately and then roll bonded together with the core, or the LPM liner, 4000 liner, core and/or waterside liner are roll bonded in the same process.

In another embodiment, the low melting point aluminum alloy has a temperature at which melting begins in the range of 510 to 560 °C and a temperature at which melting is completed in the range of 565 to 585 °C.

In another embodiment, Zn present in the low melting point aluminum alloy in the pre-braze condition is distributed into the 4XXX aluminum alloy adjacent to the low melting point aluminum alloy in the post-braze condition and into the core.

In another embodiment, the remainder of the low melting point aluminum alloy in the post braze condition forms an anodic corrosion resistant layer protecting the core.

In another embodiment, the corrosion resistant layer has a corrosion potential difference between the surface and the core in the range of 15 to 150 mV.

In another embodiment, the sheet material is formed of a first portion and further comprises a second sheet material formed of an aluminum alloy, wherein the first portion is brazed to the second portion to form an assembly.

In another embodiment, the assembly is a heat exchanger.

In another embodiment, the brazing method comprises:

providing a first part formed of a sheet material having a core of 2XXX, 3XXX, 5XXX or 6XXX aluminum alloy and a composite braze liner having a low melting point aluminum alloy layer and a 4XXX aluminum alloy layer; providing a second part formed of an aluminum alloy; placing the first portion in contact with the second portion; heating the first part and the second part; melting the low melting point aluminum alloy before melting the 4XXX aluminum alloy; melting the 4XXX aluminum alloy and forming a mixed molten alloy of the low melting point aluminum alloy and the 4XXX aluminum alloy; forming a braze joint between the first portion and the second portion from the mixed molten alloy; and cooling the mixed molten alloy.

In another embodiment, the heating step is performed in a controlled atmosphere and further comprises applying Nocolok flux to at least one of the first portion and the second portion to remove oxides from a surface thereof.

In another embodiment, the maximum temperature is maintained for less than 5 minutes.

In another embodiment, the low melting point aluminum alloy starts melting at a temperature less than 560°C.

In another embodiment, the core has a composition comprising at least one of 0.2 to 1.0 wt % Mg, 0.4 to 2.6 wt % Cu, and/or 0.1 to 1.0 wt % Si.

In another embodiment, the diffusion step includes diffusing Si, Cu, Zn into the 4XXX aluminum alloy and reducing the temperature at which the 4XXX aluminum alloy melts.

In another embodiment, the sheet material comprises a core of 2XXX, 3XXX, 5XXX or 6XXX aluminum alloy; A composite braze liner having a low melting point aluminum alloy layer and a 4XXX aluminum alloy layer, wherein the low melting point aluminum alloy has a lower melting point than the 4XXX aluminum alloy.

In another embodiment, the 4XXX aluminum alloy is disposed on the core and the low melting point aluminum alloy is disposed on the 4XXX aluminum alloy distal to the core, or the low melting point aluminum alloy is disposed on the core and the low melting point aluminum alloy is disposed on the core. 4XXX aluminum alloy is disposed on the low melting point aluminum alloy distal to the core, or the 4XXX aluminum alloy comprises a first 4XXX aluminum alloy layer and a second 4XXX aluminum alloy layer, wherein the first 4XXX aluminum alloy layer is An alloy layer is disposed on the core and the low melting point aluminum alloy is disposed on the first 4XXX aluminum alloy layer distal to the core, and the second 4XXX aluminum alloy layer is disposed on the first 4XXX aluminum alloy layer. disposed on the low melting point aluminum alloy layer distal to the layer.

In another embodiment, the sheet material of any of the foregoing embodiments further comprises at least one aluminum alloy distal layer disposed on the core at a side distal to the composite braze liner and/or the at least one aluminum alloy distal layer. wherein the distal layer of is a 4XXX aluminum alloy layer and/or the at least one distal layer is a second composite braze liner and/or the at least one distal layer is a water side liner and/or the water side liner is between 1.0 and 15 It is a 7XXX aluminum alloy with zinc in the weight percent range.

In another embodiment, in the sheet material of any of the preceding embodiments, the low melting point aluminum alloy has a melting point in the range of 510°C to 560°C.

In another embodiment, in the sheet material of any of the preceding embodiments, the low melting point aluminum alloy comprises 4.0 to 12.0 weight percent Si, 0.1 to 1.0 weight percent Fe, 1.0 to 5.0 weight percent Cu, and 5.0 to 20.0 weight percent. % by weight of Zn and/or the low melting point aluminum alloy has a solidus in the range of 510°C to 560°C and a liquidus in the range of 565°C to 585°C and/or the amount of Si in the low melting point aluminum alloy is 4 to 9 wt. % range and/or the amount of Zn in the low melting point aluminum alloy ranges from 6 to 18 weight percent.

In another embodiment, in the sheet material of any of the preceding embodiments, the composite braze liner comprises 4.0-12.0 wt% Si, 0.1-1.0 wt% Fe, ≤2.0 wt% Cu, 1.0-6.0 wt% Zn and the composite braze liner has a solidus line of 515 ° C to 575 ° C and a liquidus line of 565 ° C to 595 ° C, or the composite braze liner contains 10.0 to 10.5 wt% Si, 0.15 to 2.0 wt% Fe, ≤0.7% by weight of Cu, ≤4.0 to 6.0% by weight of Zn, and the composite braze liner has a solidus line of 550 °C to 575 °C and a liquidus line of 575 °C to 590 °C.

In another embodiment, in the sheet material of any of the preceding embodiments, the core comprises 0.10-1.2 wt% Si, 0.15-0.5 wt% Fe, 0.40-3.5 wt% Cu, 0.10-1.8 wt% Mn. , 0.20 to 1.85% by weight of Mg, ≤0.01% by weight of Cr, ≤0.20% by weight of Zn, and ≤0.20% by weight of Ti, and the core has a solidus line of >590 ° C and a liquidus line of >650 ° C. Alternatively, the core may contain 0.10 to 0.90 wt% of Si, 0.15 to 0.5 wt% of Fe, 0.40 to 2.60 wt% of Cu, 0.10 to 1.55 wt% of Mn, 0.20 to 1.0 wt% of Mg, ≤0.01 wt% of Cr, ≤0.20% by weight of Zn, and ≤0.20% by weight of Ti, and the core has a solidus of >590°C and a liquidus of >650°C.

In another embodiment, in the sheet material of any of the preceding embodiments, the core comprises at least one strengthening element selected from Si, Cu, Mn and Mg and/or the Mg present in the core (pre-braze) is 0.2 to 1.85 wt%, Cu in an amount of 0.4 to 3.5 wt%, Mn in an amount of 0.1 to 1.8 wt%, and Si in an amount of 0.1 to 1.2 wt%.

In another embodiment, in the sheet material of any of the preceding embodiments, the clad to core ratio of the composite braze liner ranges from 4 to 18% and/or

In the composite braze liner, the ratio of the thickness of the low melting point aluminum alloy to the thickness of the 4XXX aluminum alloy ranges from 5 to 50% and/or

The LPM liner and 4000 liner are roll bonded and manufactured separately and then roll bonded together with the core, or the LPM liner, 4000 liner, core and/or waterside liner are roll bonded in the same process.

In another embodiment, the sheet material of any of the preceding embodiments, wherein the low melting point aluminum alloy has a temperature at which melting begins in the range of 510 to 560 °C and a temperature at which melting is completed in the range of 565 to 585 °C. .

In another embodiment, in the sheet material of any of the foregoing embodiments, the Zn present in the low melting aluminum alloy in the pre-braze state into the 4XXX aluminum alloy adjacent to the low melting aluminum alloy in the post-braze state and The remainder of the low melting point aluminum alloy distributed into the core and/or in the post-braze state forms an anodic corrosion resistant layer protecting the core and/or the corrosion resistant layer between the surface and the core 15 to 150 mV of corrosion potential.

In another embodiment, the sheet material of any of the foregoing embodiments, wherein the sheet material is formed of a first portion and further comprises a second sheet material formed of an aluminum alloy, wherein the first portion is formed of the second portion. brazed to form an assembly and/or the assembly is a heat exchanger.

In another embodiment, the brazing method comprises:

providing a first part formed of a sheet material having a core of 2XXX, 3XXX, 5XXX or 6XXX aluminum alloy and a composite braze liner having a low melting point aluminum alloy layer and a 4XXX aluminum alloy layer; providing a second part formed of an aluminum alloy; placing the first portion in contact with the second portion; heating the first part and the second part; melting the low melting point aluminum alloy before melting the 4XXX aluminum alloy; melting the 4XXX aluminum alloy and forming a mixed molten alloy of the low melting point aluminum alloy and the 4XXX aluminum alloy; forming a braze joint between the first portion and the second portion from the mixed molten alloy; and cooling the mixed molten alloy.

In another embodiment, in any of the preceding embodiments, the heating step is performed in a controlled atmosphere and a Nocolok flux is applied to at least one of the first portion and the second portion to remove oxides from the surface thereof. additional steps are included.

In another embodiment, in any of the preceding embodiments, the maximum temperature is maintained for less than 5 minutes and/or the low melting point aluminum alloy begins melting at a temperature less than 560°C.

In another embodiment, in any of the preceding embodiments, the core has a composition comprising at least one of 0.2 to 1.0 wt% Mg, 0.4 to 2.6 wt% Cu, and/or 0.1 to 1.0 wt% Si, and / or the diffusion step diffuses Si, Cu, Zn into the 4XXX aluminum alloy, thereby reducing the temperature at which the 4XXX aluminum alloy melts.

For a more complete understanding of the present disclosure, reference is made to the following detailed description of exemplary implementations considered in conjunction with the accompanying drawings.
1A is a schematic diagram of a brazing sheet material according to an embodiment of the present disclosure.
1B is a schematic diagram of a brazing sheet material according to another embodiment of the present disclosure.
1C is a schematic diagram of a brazing sheet material according to another embodiment of the present disclosure.
2A is a cross-sectional view of a brazing sheet material according to an embodiment of the present disclosure.
2B is a cross-sectional view of a brazing sheet material according to an embodiment of the present disclosure.
3A is a graph of a differential scanning calorimetry (DSC) test for a low melting point alloy according to an embodiment of the present disclosure.
3B is a graph of a differential scanning calorimetry (DSC) test for a low melting point alloy according to an embodiment of the present disclosure.
4A is a graph of a differential scanning calorimetry (DSC) test for a four-layer brazing sheet having a low melting point alloy according to an embodiment of the present disclosure.
4B is a graph of a differential scanning calorimetry (DSC) test for a four-layer brazing sheet having a low melting point alloy according to an embodiment of the present disclosure.
5A is a graph of elemental distribution within a four-layer brazed composite sheet having a low melting point alloy according to an embodiment of the present disclosure, prior to brazing.
FIG. 5B is a graph of elemental distribution within the four-layer brazed composite sheet of FIG. 5A after brazing.
6 is a graph of the distribution of elements Cu, Zn and Mg in the brazing sheet of FIG. 5B after brazing.
7 is a graph of corrosion potential within the composite brazing sheet of FIG. 6;
8A is a cross-sectional view of a braze joint formed by brazing a brazing sheet according to an embodiment of the present disclosure.
8B is a cross-section of a braze joint formed by brazing a brazing sheet according to an embodiment of the present disclosure.

The heat exchanger structure may be formed from an aluminum alloy sheet material, comprising at least two layers, a core layer of eg 2000, 3000, 5000 or 6000 series aluminum as a base alloy, and eg a 4000 series base alloy. It has a formed braze layer/braze liner. This type of material can be described as a brazing sheet. Before assembling the heat exchanger structure through brazing, the surface of the braze layer may be layered with an oxide film, such as Al oxide, Mg oxide, etc., for example, through a manufacturing process and exposure to the atmosphere. The oxide layer is removed before or during the brazing process to ensure that the oxide barrier between the elements to be joined does not contaminate or deteriorate the joint and that the filler metal "wets" or bridges the surfaces to be joined to create a good joint. The present disclosure recognizes that in the vacuum brazing process undesirable oxide layers are broken by evaporation of Mg present in the braze liner or core of the brazing sheet. Mg is an important alloying element in aluminum alloy brazing sheets to increase material strength, so the vacuum brazing process can utilize the presence of Mg in the brazing sheet to remove oxides on component surfaces and strengthen the final brazed heat exchanger assembly. .

In a controlled atmosphere brazing (CAB) process, brazing is performed in an inert atmosphere that largely excludes ambient oxygen, thus reducing oxides formed during the brazing process. The oxide film(s) already present on the brazing sheet are removed by a flux, such as Nocolok flux. The flux can dissolve the oxide film on the surface of the brazing sheet and promote wettability of the surfaces to be bonded. Nocolok flux has limited solubility of Mg oxide and limited ability to remove Mg oxide. Additionally, Mg diffused to the surface during the brazing process can react with F and K in the flux, which can change the flux composition by forming MgF ₂ , KMgF ₃ , and K ₂ MgF ₄ , increase the flux melting point and increase the oxide Negatively affects the removal of membranes. Nocolok fluxes containing Cs have been developed for aluminum alloys containing Mg, such as 6063. Cs flux can effectively break and remove the MgO film, thus ensuring good brazing potential of Mg-containing brazing sheets, but it is about three times more expensive than Nocolok flux and is therefore not preferred over Nocolok by heat exchanger manufacturers. As a result, Mg-containing aluminum alloys are not widely used to make heat exchangers made by the CAB process.

An aspect of the present disclosure is a composite braze liner (CBL) that allows aluminum alloys containing Mg to be brazed assembled using Nocolok flux in a CAB process. More specifically, the CBL includes a low melting point (LMP) aluminum alloy layer bonded to a 4XXX braze liner. When heated in a CAB furnace, the LMP layer will melt at a lower temperature before the 4XXX braze liner melts during the brazing process. The liquid metal produced from the LMP layer can then accelerate Si diffusion within the LMP alloy and adjacent 4XXX liner. Additionally, alloying elements such as Cu and Zn diffused from the LMP alloy into the 4XXX braze liner can lower the melting point of the 4XXX liner. Both of these factors can accelerate the melting and flow of the 4XXX braze liner filler metal, and compared to the conventional 577°C to 613°C temperature range of today's widely used CAB brazing process, the brazing process can, for example, achieve about 565°C. to 590 °C to allow for rapid completion in the lower temperature range. In one embodiment, the upper limit of the temperature range lowered according to the present disclosure is less than 577°C. LMP also has the positive effect of reducing the time required for the brazing from about 25 to 45 minutes in the case of conventional processes to a reduced time of about 15 to 30 minutes according to one embodiment of the present disclosure. In one embodiment, the brazing time according to the present disclosure is less than 25 minutes. A fast brazing process in the low temperature range can reduce the diffusion of Mg to the surface of the brazing sheet components to be bonded, i.e. reducing the MgO formation and the reaction of Mg with the Nocolok flux, thus reducing the negative effect of Mg on the brazing ability. can reduce Thus, the present disclosure can braze heat exchanger components made of Mg-containing aluminum alloys using Nocolok flux in a CAB process. In addition, the brazing process performed at a lower braze temperature allows the use of other alloying elements, such as Si, Cu, etc., in the core alloy, which raises the solidus temperature of the core, e.g., to that required for conventional CAB brazing without melting. Reduce the temperature to an unbearable level <590 °C. Thus, the present disclosure enables CAB brazing of components, for example tubes, tanks and/or fins of heat exchangers made of high strength brazing sheet materials.

A new material that can be bonded by a CAB according to the present disclosure is, for example, a high-strength material, such as a significant amount of magnesium, for example in the range of 0.3 to 1.0 weight percent, or more, for example up to 1.85%, relative to the core. Including up to weight percent. The use of high-strength materials allows for thinner gauge brazing sheets, resulting in lighter, better-performing heat exchangers. The CBL composition and clad ratios disclosed herein can be selected such that the LMP layer, after mixing and melting with the 4XXX brazing layer, can form a protective layer to prevent corrosion of cores in use, for example, as automotive radiators. there is. Brazing sheets according to the present disclosure also allow heat exchanger manufacturers to use a low temperature brazing process, which is easy to control and saves energy and manufacturing costs.

1A shows a core 12 having a base composition of 2000, 3000, 5000 or 6000 series aluminum alloy, a braze liner (layer) 14 having a base composition of 4XXX (4000) series aluminum alloy, and a low melting point (LMP) layer. A brazing sheet material 10 having a (liner) 16 is shown. The combination of the braze liner 14 and the LMP layer 16 can be identified as a component of a composite braze liner (CBL) 18 . In FIG. 1A , LMP layer 16 is an outer liner/layer disposed on top of 4XXX braze liner 14 on the first side of core 12 . On the second side of the core 12, there may be another CBL 18, a single braze liner, or a few side liner, or no liner, depending on the application. The water side liner may be a 3000 series alloy or a 7000 alloy with the addition of Zn, for example 1.0 to 15.0 weight percent Zn.

1B shows a brazing sheet material 20, such as the brazing sheet material 10 of FIG. 1A , with a core 22 and a braze liner 24, but the LMP layer 26 is composed of a core 22 and a 4XXX It is positioned between the braze liners 24 to create a CBL 28 having an orientation reversed to that of the CBL 18 of FIG. 1A. Due to the orientation and location of the CBL 28, the LMP layer 26 can be described as an inner liner between the 4XXX braze liner 24 and the core 22. Similarly, on the second side of the core 22, there may be another CBL 28, a single braze liner, or a few side liner, or no liner, depending on the application.

1C shows a brazing sheet material 30, such as the brazing sheet materials 10 and 20 of FIGS. 1A and 1B, having a core 32, a two-part braze liner 34A, 34B, and an LMP layer ( 36) is located between the two pieces of braze liners 34A and 34B, so that the CBL 38 has three layers. An optional layer 39, indicated by dotted lines, may be provided on the core 32 opposite the CBL 38, and depending on the application, a CBL such as CBL 38, 28 or 18, an anode layer for corrosion protection, There may or may not be an anode layer covered by the CBLs 18, 28, 38 (there is no clad layer on this side of the core).

Examples of LMP alloys used in 4000 series braze liners (14, 24, 34A, 34B), in this case 4047 alloy and bonded layers (16, 26, and/or 36), expressed in weight percent, balance being aluminum. It was tested as shown in Table 1. The indicated solidus and liquidus lines were calculated based on the composition of each alloy in Table 1.

All of the LMP layer compositions in Table 1 have low solidus and liquidus lines that initiate melting of the composite braze liners (CBLs) 18, 28, 38 at low temperatures. Liquefied metal in the LMP layers 16, 26, 36 can accelerate Si diffusion and melting. The alloying elements of the LMP layers 16, 26, 36, including but not limited to Zn and Cu, can diffuse into the adjacent 4XXX liners 14, 24, 34A, 34B, so that the overall composite braze liner CBL 18, 28, 38) can melt rapidly at lower temperatures than conventional 4XXX braze liners. The LMP layers 16, 26, 36 should have good machinability and similar metal flow in the rolling process as do the braze layers 14, 24, 34A, 34B, all of which would deform in a similar manner during rolling into gauges and otherwise If not, the gauge should indicate compliance. In addition, the clad ratio of the composite braze liner (CBL) indicates that the final composition of the CBL (18, 28, 38) (i.e., a mixture of LMP liner and 4XXX liner) after melting has good strength and corrosion resistance comparable to a braze joint formed with only 4XXX liner. It is selected to form a good braze joint with properties. According to the present disclosure, composite liner (CBL) residue left after brazing provides corrosion protection to the core to ensure good service life of the heat exchanger.

In one embodiment, the LMP layer comprises 4.0-12.0 wt% Si, 0.1-1.0 wt% Fe, ≤5.0 wt% Cu, ≤0.1 wt% Mn, ≤0.01 wt% Cr, 5.0-20.0 wt%. of Zn, and ≤ 0.02% by weight of Ti, and may have a solidus line in the range of about 510 °C to 560 °C and a liquidus line in the range of 565 °C to 585 °C.

In another embodiment, the amount of Si in the low melting point aluminum alloy ranges from 4 to 9 weight percent. In another embodiment, the amount of Zn in the low melting point aluminum alloy ranges from 6 to 18 weight percent.

Table 2 shows two exemplary compositions, CBL1 and CBL2, produced from a 4047 liner combination of the LMP alloys (L1 and L2) from Table 1, expressed in weight percent, balance aluminum. Compositions CBL1 and CBL2 were determined based on calculations without considering diffusion, and the solidus and liquidus lines were calculated based on the composition at the time of casting.

In one embodiment, the CBL may have a composition having 4.0-12.0 wt% Si, 0.1-1.0 wt% Fe, ≤2.0 wt% Cu, ≤0.1 wt% Mn, 1.0-6.0 wt% Zn, , the composite braze liner has a solidus line of 515°C to 575°C and a liquidus line of 565°C to 595°C.

In another embodiment, the composite braze liner comprises 10.0-10.5 wt% Si, 0.15-1.0 wt% Fe, ≤1.0 wt% Cu, ≤0.1 wt% Mn, 4.0-6.0 wt% Zn; , the composite braze liner has a solidus line of 550°C to 575°C and a liquidus line of 575°C to 590°C.

2A and 2B show the microstructure of the composite samples of the brazing sheets 20 and 10 shown in FIGS. 1B and 1A, respectively, with FIG. 2A showing the LMP layer 26 as an inner liner and FIG. ) as an outer liner. Samples were prepared in a laboratory scale hot rolling and cold rolling process using process parameters similar to commercial product manufacturing processes. The LMP layers 16, 26, braze liners 14, 24, and cores 12, 22 are well bonded to their respective adjacent laminates without any defects.

Solidus and liquidus were tested for exemplary compositions of core alloys according to the present disclosure and the results are shown in Table 3. Some of the core alloys, such as C3, C4, and C10, contain high levels of Mg that are challenging to braze in a CAB process with Nocolok fluxes. Some of the core alloy compositions include high Cu and Mg, for example C3 and C10, which have low melting points and are expected to start melting during the CAB process.

In one embodiment, the core comprises 0.10-1.2 wt% Si, 0.15-0.5 wt% Fe, 0.40-3.5 wt% Cu, 0.10-1.8 wt% Mn, 0.20-1.85 wt% Mg, ≤0.01 wt%. % Cr, ≤0.2% Zn, and ≤0.2% Ti, the core has a solidus >590°C and a liquidus >650°C.

In another embodiment, the core comprises 0.10-1.0 wt % Si, 0.15-0.5 wt % Fe, 0.40-3.0 wt % Cu, 0.10-1.7 wt % Mn, 0.20-1.5 wt % Mg, ≤0.2 It has weight percent Zn, and <0.2 weight percent Ti, and has a solidus >590°C and a liquidus >650°C.

In one embodiment, the core has at least one strengthening element selected from Mg, Cu, Si, Mn.

In another embodiment, Mg is present in the core in an amount of 0.2 to 0.8 wt%, Cu is in an amount of 1.5 to 2.5 wt%, and Si is 0.2 to 1.0. 3A and 3B are graphs showing the results of differential scanning calorimetry (DSC) tests performed to determine the melting points of two low melting point aluminum alloys (LMPs), namely alloys L1 and L2 in Table 1, respectively (50 , 52), respectively. In the DSC test graphed in FIGS. 3A, 3B, 4A, 4B, 5A and 5B, heating was performed at a rate of 20° C. per minute. Graph 50 of FIG. 3A indicates that heat flow begins at 928.4F (497°C), indicating that alloy L1 has begun to melt. Heat absorption peaks at 1001.1 F (538° C.), indicating large amounts of LMP metal melting. After that, the heat absorption started to decrease, but then it started to rise with another peak at 1069F (576°C) where the rest of the Al-Si eutectic metal seemed to start melting. The melt was complete at 1089.6F (588°C).

Graph 52 of FIG. 3B shows that the melting of alloy L2 started at 945.4F (507°C) and reached a peak at 1012.7F (545°C). After the melting of the metal slowed down, a second peak started at 1068F (575.5°C) where the Si eutectic metal began to melt. Melting of the composite braze liner was complete at 1109.2 (598°C).

Table 4 shows the DSC test results for the 4-layer material samples. Sample A had CBL1 (in Table 2) on one side of core C3 (Table 3) and 4047 on the other side. Sample B had CBL2 (Table 2) on one side of the core and 4047 on the other side. The clad ratio of the CBL1 and CBL2 and 4047 layers was 15%, and the core was Alloy C3 in Table 3. The structure and composition of the laminates of Samples A and B are shown in Table 4, expressed as weight percent and balance aluminum.

Samples A and B of Table 4 assembled the liner and core together; reheat to hot rolling temperature; hot rolling at a temperature in the range of 450-515C; It was prepared by annealing followed by rolling to final gauge or by cold rolling to thin gauge for final annealing.

4A shows the DSC results for Sample A as a graph 54, where the first melt (inner liner) of Sample A with CBL1 started at 1026.1F (552.3°C) and the second melt was about 1062.1F (572.2°C). ) was started. Melting of the braze liner of Sample A, which included CBL1 on one side and 4047 on the other side, was complete at 1104.4F (598°C).

FIG. 4B graphs 56 the DSC results for sample B, where the first melt (inner liner) started at 1037.7F (559°C) and the second melt started at about 1060.9F (571.6°C). For Sample B, which contained both CBL and 4047, melting of the braze liner was complete at 1106.2 F (596.8 C).

As shown in graphs 54 and 56, the LMP layer in the composite begins to melt at a higher temperature than the monolithic alloy due to compositional changes associated with diffusion of alloying elements such as Cu, Zn, etc. in both fabrication and brazing processes. As mentioned above, the liquid metal melting initiated at 552-559°C accelerates the dissolution of Si in the 4047 braze liner and the Cu/Zn diffused into the 4047 liner will lower the melting point of the liner and the braze liner will start melting at a lower temperature. make it possible

5A shows a graph 58 of pre-braze alloy element distribution within the layer: a table with LMP 60, braze liner 62, core 64, and braze liner 66 of clad brazing sheet 68. Same as sample A in 4. LMP 60 and braze liner 62 create composite braze liner CBL 18 (FIG. 1A), where low melting point liner 60 is an outer liner. Cu and Zn levels are high in the thin layer of LMP liner 60 .

The alloying element distribution of the post-braze sample (Sample B in Table 4) is shown in FIG. 5B, where layers 72, 74, 76 and 78 are the layers LMP 60 of FIG. 5A, the braze liner 62, the core ( 64) and braze liner 66, but in a post-brazed condition. Diffusion was simulated based on solid-state diffusion in the braze thermal cycle, and the Zn and Cu levels were significantly lower than the initial levels of the pre-braze state. These Cu and Zn levels suggest an acceptable level of corrosion resistance. The distribution of alloying elements in the actual post-braze sample was in good agreement with the simulation. In FIG. 5a, Zn is 15% and Cu is about 2.35% on the surface, but in FIG. 5b, Zn is 2.3 to 2.4% and Cu is 0.65 to 0.7% on the surface.

6 shows a graph 82 of the post-braze Cu, Mg, and Zn distribution within the layers CBL 84, core 86, and inner braze liner 88 of a brazing sheet 90, where the LMP liner is Alloy C3 of Table 2 was used as the core alloy having the composition L2 of Table 1 and having an outer clad liner of alloy 4047. The locations on the two sides of the braze joint formed between adjacent brazing sheets 90 were tested (indicated as -1 and -5 in the legend of FIG. 6).

7 shows a composite brazing sheet having an LMP layer 96 (forming CBL 2 in Table 2) as an outer liner, a 4000 series layer 98, a core 100, and an outer liner 102 of a 4000 series alloy. A graph 94 of corrosion potential distribution within material 104 is shown. To evaluate the corrosion performance of the post-braze material 104, the corrosion potential was simulated based on the alloying element distribution of the post-braze material. The corrosion potential on the sample surface has a corrosion potential of about -900 mV, which is anodic to the core and thus can provide good corrosion protection to the core.

This disclosure discloses a new material known as CBL, which has a thin layer of LMP aluminum alloy bonded with a normal 4XXX braze liner alloy, such as 4343, 4045, 4047, etc. In the early stages of the braze process, before the LMP aluminum liner starts melting, alloying elements such as Cu and Zn will diffuse into the adjacent 4XXX braze liner, which lowers the melting point of the 4XXX braze liner alloy. If the low-melting alloy layer starts melting, for example at about 510 °C, the liquid metal can accelerate the Si eutectic metal melting because Si diffusion in the liquid metal is much faster than in the solid metal. . In this way, the 4XXX braze liner can be rapidly melted at a temperature lower than its processing temperature, i.e., 577°C.

In accordance with the present disclosure, a braze process was developed for brazing samples at low temperatures. The sample was subjected to a short brazing cycle of about 8-12 minutes and heated to a temperature of about 560°C to 575+/-5°C. In short brazing cycles at low temperatures, less Mg diffusion from the core to the brazing surface occurs, which reduces the reaction between Mg and F/K in the flux and the formation of Mg oxides. The reduced diffusion of Mg compared to brazing at higher temperatures and/or for longer times facilitates the operation of Nocolok fluxes for Mg-rich core alloys, effectively dissolving surface oxides present on the brazing surface. and can be removed.

8A shows a braze joint 110 between a brazing sheet material 112 and a non-clad fin 114 according to the present disclosure. A brazing sheet 112 was formed on the first side of the core 116 with a CBL 118 overlaid with 4047 clad and alloy layer L1 in Table 1 as an inner liner at a total clad ratio of 15%. The core alloy was Alloy C3 in Table 2. A braze liner 120 of alloy 4047 was covered on the second side of the core with a 15% clad ratio. Corrugated non-clad pins 114 were assembled on both sides of the brazing sheet 112 (only one side shown in FIG. 8A). A sample with fins was emulsified with Nocolok flux in the CAB process and brazed at 575°C. A braze joint was formed on the composite braze liner CBL 118 as shown, but not on the opposite side of the core 116 (not shown) covered only with the 4047 liner.

8B shows a braze joint 130 between a brazing sheet material 132 and a non-clad fin 134 according to the present disclosure. A brazing sheet 132 was formed on the first side of the core 136 with a CBL 138 clad with a 4047 braze liner and alloy layer L2 in Table 1 as an outer liner, with a total clad ratio of 15%. The core alloy was Alloy C3 in Table 2. A braze liner 140 of alloy 4047 was applied to the second side of the core 136 with a 15% clad ratio. Corrugated non-clad pins 134 were assembled on both sides of the brazing sheet 132 (only one side shown in FIG. 8B). A sample with pins 134 was emulsified with Nocolok flux in the CAB process and brazed at 575°C. A braze joint was formed on the side of the composite braze liner CBL 138 as shown, but not on the opposite side of the core 136 (not shown) covered only with 4047 liner. CBLs, eg 118, 138, can be rolled together in a hot rolling process with other liners and cores using normal rolling processes. It can also be formed by other techniques and processes, including, but not limited to, a coating technique of coating a layer of LMP aluminum alloy powder onto a 4XXX braze liner, a thermal spray technique of spraying a layer of LMP aluminum alloy onto a 4XXX braze liner, and the like. It doesn't work.

Sample materials according to the present disclosure exhibited high post braze strength as shown in Table 5. Samples were prepared up to 0.20 mm gauge with 10% water side liners containing high Zn ranging from 6% to 12% by weight. They were prepared in the H14 or H24 temper. The post-braze samples in Table 5 were either naturally or artificially aged.

The compositional ranges given above for LMP, CBL, and core include all intervening values. For example, in an embodiment of the LMP having a composition of 4.0 to 12.0 wt% Si, 0.1 to 1.0 wt% Fe, 1.0 to 5.0 wt% Cu, ≤0.1 wt% Mn, and 5.0 to 20.0 wt% Zn. 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, etc. in increments of 0.1 up to 12.0 and All intermediate amounts of Si, 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0 to 5.0 in 0.1 weight percent increments, or any intermediate value of Fe, 1.0 to 5.0 in 0.5 weight percent increments. or any intermediate value of Cu, from 0.0 to 0.1 in increments of 0.01 weight percent, or any intermediate value of Mn, 5.0, 5.5, 6.0. 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5. 10.0, 10.5, 11.0, 11.5, 12.0, 12.5, 13.0, 13.5, 14.0, 14.5, 15.0, 15.5, 16.0, 16.5, 17.0, 17.5, 18.0, 18.5, 19.0, 19.5 or 2 0.0% by weight or any intermediate value of Zn include

In a further example of an alternative embodiment according to the present disclosure, a composition of 4.0-12.0% Si, 0.1-1.0% Fe, ≤2.0% Cu, ≤0.1% Mn, 1.0-6.0% Zn, by weight. Compositional ranges for embodiments of CBL having, as in the previous paragraph, include the median value of all increments varying by 0.01% by weight for each element over the entire recited range.

In a further example of an alternative embodiment according to the present disclosure, 0.10-1.2 wt % Si, 0.15-0.5 wt % Fe, 0.40-3.5 wt % Cu, 0.10-1.8 wt % Mn, 0.20-1.85 wt % The compositional ranges for embodiments of the core having a composition of Mg, ≤0.2 wt% Zn, and ≤0.2 wt% Ti include all intervening values for each element throughout the entire range as in the previous paragraph.

The present disclosure describes a composite braze liner that enables brazing of heat exchanger assemblies at temperatures lower than those widely used in industry today. This low-temperature brazing adds high levels of alloying elements with strengthening properties, such as Si, Cu, and Mg, and allows them to withstand melting point depression. In addition, it also reduces energy consumption when brazing the heat exchanger assembly.

In another embodiment, the present disclosure may braze Mg-rich brazing sheet products using normal fluxes such as Nocolok fluxes in a controlled atmosphere brazing (CAB) process to achieve high strength. In another embodiment, the composition and clad ratio of the composite braze liner can be designed to achieve a material with good corrosion resistance properties.

This disclosure provides standard abbreviations for elements appearing on the periodic table of elements, such as Mg (magnesium), O (oxygen), Si (silicon), Al (aluminum), Bi (bismuth), Fe (iron), Zn (zinc). , Cu (copper), Mn (manganese), Ti (titanium), Zr (zirconium), F (fluorine), K (potassium), Cs (cesium), etc. are used.

The drawings constitute part of this specification, include exemplary implementations of the present disclosure, and illustrate various objects and features thereof. In addition, any measurements, specifications, etc. shown in the figures are for illustrative purposes only and are not intended to be limiting. Accordingly, specific structural and functional details disclosed herein should not be construed as limiting, but only as a representative basis for teaching those skilled in the art to the various applications of the present invention.

Among the advantages and improvements disclosed, other objects and advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings. Detailed embodiments of the present invention are disclosed herein. However, it should be understood that the disclosed embodiments are merely illustrative of the invention, which may be embodied in a variety of forms. Further, each of the examples given in connection with various embodiments of the present invention is illustrative and not limiting.

Throughout the specification and claims, the following terms take on the meanings explicitly associated herein unless the context clearly dictates otherwise. The phrases “in one embodiment” and “in some embodiments” as used herein do not necessarily refer to the same embodiment(s), but may refer to the same embodiment(s). Also, the phrases “in other embodiments” and “in some other embodiments” as used herein do not necessarily refer to other embodiments, but may refer to other embodiments. Thus, as discussed below, various embodiments of the present invention can be readily combined without departing from the scope or spirit of the present invention.

Also, as used herein, the term "or" is the inclusive "or" operator and is equivalent to the term "and/or" unless the context dictates otherwise. The term “based on” is not exclusive and may be based on additional factors not described unless the context dictates otherwise. Also, throughout the specification, the meanings of “a” and “an” include plural references. The meaning of “within” includes “within” and “above”.

Although a number of embodiments of the present invention have been described, it will be appreciated that these embodiments are illustrative only and not limiting, and many variations may become apparent to those skilled in the art. Further, the various steps may be performed in any desired order (and any desired steps may be added and/or any desired steps may be removed). All such variations and modifications are intended to be included within the scope of the present claims.

Claims (20)

As a brazing sheet,
a core of 2XXX, 3XXX, 5XXX or 6XXX aluminum alloy;
a composite braze liner adjacent to the core;
including,
The composite braze liner,
4XXX aluminum alloy layer; and
A low melting point aluminum alloy layer connected to the 4XXX aluminum alloy layer
including,
The low melting point aluminum alloy layer has a melting point lower than that of the 4XXX aluminum alloy layer,
The low melting point aluminum alloy contains 4-12 wt% Si, 0.1-1.0 wt% Fe, 1.0-5 wt% Cu, 0.1 wt% or less Mn and 5-20 wt% Zn,
The brazing sheet according to claim 1, wherein the balance of the low melting point aluminum alloy consists of aluminum and incidental impurities. The brazing sheet according to claim 1, wherein the 4XXX aluminum alloy layer is disposed on the core and the low melting point aluminum alloy layer is disposed on the 4XXX aluminum alloy layer. The brazing sheet according to claim 1, wherein the low melting point aluminum alloy layer is disposed on the core and the 4XXX aluminum alloy layer is disposed on the low melting point aluminum alloy layer. The brazing sheet of claim 1 comprising a water side liner. 5. The brazing sheet of claim 4, wherein the water side liner comprises 1.0-15% by weight of Zn. The brazing sheet according to claim 1, wherein the low melting point aluminum alloy layer has a solidus line of 560°C or less. delete The brazing sheet according to claim 1, wherein the core has a solidus line greater than 590°C and the core has a liquidus line greater than 650°C. 9. The method of claim 8, wherein the core comprises 0.10-1.2 wt% Si, 0.15-0.5 wt% Fe, 0.40-3.5 wt% Cu, 0.10-1.8 wt% Mn, 0.20-1.85 wt% Mg, ≤ A brazing sheet comprising 0.01% by weight of Cr, ≤0.20% by weight of Zn and ≤0.20% by weight of Ti. providing a first part formed from the brazing sheet of any one of claims 1 to 6, 8 and 9;
providing a second part formed of an aluminum alloy;
applying Nocolok flux to at least one of the first portion and the second portion to remove oxides from the surface thereof;
placing the first portion in contact with the second portion;
heating the first part and the second part in a controlled atmosphere;
melting the low melting point aluminum alloy layer before the 4XXX aluminum alloy is melted;
melting the 4XXX aluminum alloy layer to form a mixed molten alloy of a low melting point aluminum alloy and a 4XXX aluminum alloy;
forming a braze joint between the first portion and the second portion from the mixed molten alloy; and
cooling the mixed molten alloy. delete delete delete delete delete delete delete delete delete delete

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